Can I use pressure washer on RV? What about decals?

Dear Dave,
Can a pressure washer safely be used on a travel trailer with non-metallic sides? What about the decals? —Lynn, 2021 Lance 1985

Dear Lynn,
There are quite a lot of variables when it comes to pressure washers and if they can or should not be used. I am not a big fan of using a pressure washer unless you know the pressure and proper tip. Then there are areas on your rig that you want to avoid hitting with any water pressure.

Pressure washers

First let’s look at pressure washers and their tips. There are literally hundreds of different portable pressure washers, starting with small electric models all the way up to industrial-size models. I ran a company called Easiwash for a friend back when the RV industry literally shut down (2011-2014). It manufactured a permanently mounted pressure washer inside fast food restaurants. I learned way more about pressure washers than I care to talk about.

There are two issues to look at when it comes to the force coming out of a unit: pressure (psi) and gallons per minute (gpm).

The unit we sold and installed had a pressure of 2000 psi. However, it had an output of 3.6 gpm, which gave it the cleaning power of a much higher pressure unit. Keep in mind the pressure listed by most manufacturers is at the pump manifold, not what comes out of the gun. Smaller electric units might list 1200 psi but actually only have less than 1000 psi. Some of the larger units can be as high as 5000 psi, which I would not recommend.

Pressure washer gun/tip

The next thing to look at is the gun or tip used. Smaller units typically have a gun that has a fixed tip that cannot be removed and adjusts the fan size (width of the spray) by rotating the sleeve. The pressure of these units is typically adjusted up and down by the unloader on the unit.

Guns or, more specifically, wands that have a quick disconnect can have a variety of tips that control the fan size and the pressure. You will find a variety of colors available at home improvement stores, and the color determines the fan size.

• White – 40 Degree
• Yellow – 15 Degree
• Black – 65 Degree
• Green – 25 Degree
• Red – 0 Degree

Pressure levels

The orifice size of the tip is what creates the pressure just like placing your thumb over the end of a garden hose. The larger the opening, the lower the pressure. The orifice size and fan degree are typically stamped on the stem of the nozzle. For example, 15050 is a 15 degree fan (yellow) with a 050 opening which would be higher pressure. 25100 would be a green tip with 100 orifice and low pressure. With our 2000 psi machine, the 15050 tip (yellow) created 2000 psi and a medium width spray, while the 15100 was only 300 psi with a wider fan. And stay away from a red tip as that will create a direct pin hole like blast and laser cut decals and sealant.

Danger, Will Robinson

I couldn’t help quoting one of my favorite TV shows. There are several areas that you want to either use a very low pressure or stay away from altogether.

Decals are simply a printed and cut vinyl material that has an adhesive backing to stick on the RV. As the decal is exposed to the sun, it dries out and will form small cracks and even peel. A direct hit from a pressure washer can peel off material or get underneath the surface and “blister” the decal, which will eventually burst and ruin the material. It is best to use low pressure and a soft brush or micro-cloth to clean them.

Windows are another area to be careful with as framed windows have weep holes at the bottom and a direct hit there will get water inside the rig. Slider windows have a thin plastic frame in the center with a felt strip, and a direct hit there will also get water into the rig.

Sidewall on the RV

The sidewall of your rig is a one-piece fiberglass material, which should be tough enough to withstand the pressure. However, if there are imperfections such as hairline cracks, pin holes, or even scratches, the pressure could penetrate and make it worse. It is important to visually inspect the material to make sure the material is in good condition. If your rig has the “Mesa” sidewall, which is the ribbed material, it will have a seam approximately every 18” that could also allow moisture to penetrate from a direct hit.

Your rig has a variety of sealants used such as butyl seal around the windows, self-leveling lap sealant on the roof, and non-leveling sealant on the corners that should be avoided as well. If the sealant has dried or pulled apart, moisture can also penetrate this area from a pressure blast. Here is a sealant guide Winnebago provides on their Class C units.

RV roofs

Many rubber roof material manufacturers recommend not using a pressure washer, rather a typical garden hose—which would only have about 60 psi—and scrubbing with a mild detergent and soft brush. Direct pressure could cut or peel the membrane, especially if there is a slight tear or pin hole already in the material.

Other areas of concern would be refrigerator vents on the roof and side, plumbing vents on the roof, and clearance/marker lights.

Recommendation for cleaning RV exterior

I have found that using a pressure washer doesn’t get the dirty “film” off the rig, and it requires scrubbing with a soft brush or micro-fiber cloth. The best method I have found is to rinse the sidewall and roof with water first and use a soap cannon with a mild detergent.

As most of my readers, know I have been a big fan of Dawn Dish Soap for many years, but have had an update of my ideas due to the high gloss gel coat and ceramic coatings. I use Mequiar’s Gold Class Car Wash cleaning product in a foam cannon, then scrub with a soft brush on a broom handle.

I can get the roof done from a ladder on the side and not crawl up on top. Keep the sides wet as you do the roof so it doesn’t dry and create a mess that will take you twice as long to rinse off.

My suggestion is to use a pressure washer under 1000 psi or a garden hose, and stay away from the decals, windows, and sealant. Use a foam cannon, soft brush, and scrub it off. You will love the clean look and reduce any moisture penetration.

 You might also enjoy this from Dave 

OK to use pressure washer to clean RV exterior?

Dear Dave,
My husband has done a terrific job of keeping our old RV looking new. The inside has been updated, and he is a mechanic so everything is kept in tiptop shape. For 15 years we lived in it full time and we have 150,000 miles on it. It is washed monthly using Johnson’s Baby Shampoo and waxed two times a year using Nu Finish. It is kept outside under a tree on our property but used at least every month now.

About a year ago we noted what looked to us like mold which seemed to be under the finish. It could not be cleaned off and was evenly distributed everywhere….

Continue reading Sherry’s question and Dave’s answer.

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Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here. 

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